Abstract:

Seven populations of the black-lipped pearl oyster, Pinctada margaritifera, from the western Pacific were assayed for allozyme variation at 17 polymorphic loci from mantle biopsies. Levels of within population variation were high (mean number of alleles per locus averaged 6.8, mean direct-count heterozygosities averaged 0.575). Gene frequencies within populations conformed to those expected under random mating. Significant genetic differentiation between populations within reef groups and additionally between the Great Barrier Reef (GBR) and the Pacific islands (Kiribati and the Cook Islands) was revealed by hierarchical F-ST analysis. The average numbers of migrants per generation (N(e)m) among the Pacific islands and among the GBR populations was 6-8 and twice that between the Pacific islands and the GBR. This suggests a relatively high gene flow among populations in Kiribati and the Cook Islands on an evolutionary time scale. However, the occurrence of significant differences in gene frequencies among populations within reef groups suggests that genetic surveys of local populations should be undertaken prior to making any transfers of pearl oysters from other reefs in order to protect these genetic resources.